Using DHCPv6 for DNS Configuration in Hosts draftietfdromsdnsconfigdhcpv600'txt

1
Using DHCPv6 for DNS Configuration in
Hostsdraft-ietf-droms-dnsconfig-dhcpv6-00.txt

• Ralph Droms

2
Problem Statement

• Describe mechanism through which host can obtain
  configuration information for clients DNS
  resolver
• List of DNS servers
• Domain name
• Domain search list
• First information is a property of the clients
  local environment other two are a property of
  the client

3
DNS Discovery Design Team report

• Evaluation criteria are loosely defined and not
  applied uniformly
• Merges two logically distinct problem into one
• Omits configuration information entry by sysadmin
  as evaluation criterion makes unstated
  assumptions about source of information returned
  to client
• Doesnt evaluate recommended solution against
  DHCP (as a solution)
• Recent progress on DHCP may have impact on design
  team report

4
DHCP for DNS Discovery

• Information-request used for two-message DHCP
  exchange (stateless DHCP)
• Transports configuration parameters without
  address assignment
• DHCP server maintains no dynamic state for each
  client
• Can be as simple as returning same three DHCP
  options to every Information-request
• Current specification uses site-scoped multicast
  for Information-request

5
Deployment Scenarios

• Stateless DHCP server in routers
• Stateless DHCP server colocated with DNS server
• Co-existence with full DHCP service
• Information-request answered by any server
• Address assignment request ignored by stateless
  DHCP server

6
Evaluation

• Scalability
• Using anycast or multicast scales as described in
  DDDT report
• Can deploy multiple DHCP servers for load
  distribution
• Placing DHCP server in router scales with router
  deployment
• Can use existing DHCP relay agent infrastructure
• Security DHCPv6 spec includes authentication
• Time to deploy
• Uses same DHCP client code
• Simple server must be developed
• Business motivation
• M bit requires implementation of DHCP client
• Simple DHCP servers deployed in IPv4 devices
  today
• Standardization
• DHCPv6 spec to go to last call immediately after
  IETF 52
• No other protocols or standards need to be changed

7
Evaluation (continued)

• Fate sharing
• DNS server list separate from DNS servers
  however, stateless DHCP server can be colocated
  with DNS server
• Domain name and domain search list must be
  configured somewhere
• Standardization
• DHCPv6 spec to go to last call after IETF 52
• No other protocols or standards need to be
  changed
• Convergence time (learning about service)
• List of DHCP servers provides reliability
• Using anycast or multicast scales as described in
  DDDT report
• Deployment based on DHCP Relay Agents requires
  configuration for redundancy
• Scenarios
• No routers deploy with DNS server
• No multicast use anycast or DHCP relay agents
• NBMA use anycast

8
Evaluation (continued)

• Convergence time (are they really different
  accessing service?)
• Using anycast or multicast scales as described in
  DDDT report
• Using DHCP relay agents requires specific
  deployment for redundancy or reconfiguration of
  relay agents
• Scenarios
• No routers deploy with DNS server
• No multicast use anycast or DHCP relay agents
• NBMA use anycast
• Configuration of client information
• Server on router or with DNS server can extract
  configuration from router or use simple, one time
  configuration
• Part of normal DHCP server configuration
• Client simplicity client uses one mechanism for
  DNS configuration whether or not using DHCP for
  address assignment

9
DHCP specification status

• DHCPv6 specification draft will go to WG last
  call immediately after IETF 52
• DHCP Information-request and use of multicast is
  included in current specification can easily add
  anycast